Effects of matrix viscoelasticity on interlaminar fracture toughness of acrylic/carbon fibre composites

The interlaminar fracture toughness of an acrylic resin/carbon fibre composite was studied in relation to the fracture toughness of the matrix. Composites were prepared by infusing the matrix monomers into the fibre stack and then letting the matrix to polymerize in-situ. The deformation rate and temperature dependence of both the plain matrix and the composite were analysed and by applying the time-temperature superposition the crack speed range was extended. The fracture toughness of the composite turned out to be higher than that of the plain matrix indicating that also other mechanisms linked to the presence of the fibres are present in the composite. The fracture toughness of the pure matrix increased with crack speed as it is expected for a viscoelastic material while the composite showed a constant value at varying crack speed. Further investigation is in due course to better analyse the damage mechanisms taking place in the composite during fracture.